Electric transducers for tension control in a winding device

ABSTRACT

A winding arrangement for controlling the tension in a filament or web being wound includes an electrical transducer comprising a first winding carried by a core of ferromagnetic material, a second winding carried by a separate core of ferromagnetic material which is spaced from said first core and a movable member of electrically conducting material which can be moved into and out of the gap between the cores and which is connected to a dancer arm resting on the web or filament to be wound. The varying output signal produced by the transducer with movement of the dancer arm is employed to control the drive means to the winding spindle in order to keep the tension in the web or filament substantially at the correct value.

United States Patent [151 3,665,270 Ayers 51 May 23, 1972 1 ELECTRIC TRANSDUCERS FOR 1 References Cited TENSION CONTROL IN A WINDING ED STATES P TENT I DEVICE 3,506,863 4/1970 Fallis [72] Inventor; p John Henry Ayers, mwesmfi 3,131,339 4/1964 Burr ..242/ 190 gland Primary Examiner-Bernard A. Gilheany [73] Asslgneez T. V. Manufacturing Limited, Sufiolk, En- Asa-8mm Examiner 1110mas Langmgland Attorney-Holcombe, Wetherill & Brisebois [22] Filed: Nov. 9, 1970 ABSTRACT [21] Appl. No.: 87,701

A winding arrangement for controlling the tension in a fila- Related US. Application Data ment or web being wound includes an electrical transducer [63] continuationdmpm of Ser No 792 698 Jan 21 comprising a first winding carried by a core of ferromagnetic I969 material, a second winding carried by a separate core of ferromagnetic material which is spaced from said first core and a [30] Foreign Application Priority Data movable member of electrically conducting material which can be moved into and out of the gap between the cores and Jan. 23, 1968 Great Britain ..3,573/68 which connected to a dancer arm resting on the web or fi]a ment to be wound. The varying output signal produced by the US. Cl. ..3l8/6, 242/190 tra du r with ovement of the dancer arm is employed to lnt.Cl ..B65h 59/38 control the drive means to the winding Spindle in Order to Field of Search ..3l8/6, 7; 242/7751, 189, 190 keep the tension in the web or fil t Substantially at the correct value.

2 Clairm, 10 Drawing Figures N FIRING 55 CIRCUIT 5/ 056. 58 l 45 c" L 54 53 4 V POWER SUPPLY Patented May 23, 1972 4 Shuts-Shoot 5 4 Shuts-Shoot 4 Patented May 23, 1972 ELECTRIC TRANSDUCERS FOR TENSION CONTROL IN A WINDING DEVICE This application is a continuation-in-part of my prior application, Ser. No. 792,698, filed Jan. 21, I969.

The present invention relates to electrical transducers for producing a variable electrical output signal in response to a mechanical movement.

According to the present invention an electrical transducer comprises a first winding carried by a core of ferromagnetic material, a second winding carried by a separate core of ferromagnetic material which is spaced from said first core, and a member of electrically conducting material which can be moved into and out of the gap between the two cores. Preferably said member is made of non-ferromagnetic material, although this is not essential.

The separation between the two coil and core assemblies is such that whenone winding of the transducer is energized by a varying electric signal, preferably an alternating signal, a voltage is induced in the other winding by means of the varying magnetic flux extending between the two windings and their respective cores, whereby an output signal can be derived from the other winding. By gradually inserting the member of electrically conducting material between the two cores, the coupling between the two coil and core assemblies can be varied until, when said member is completely inserted between the cores, the coupling between them is at a minimum and preferably substantially zero. Thus, the output signal from the second coil and core assembly can be varied between its maximum and minimum values by variation of the physical position of the member in relation to the gap between the two cores.

The transducer according to this invention may be used in any application where it is desired to produce an electrical output signal which varies in dependence upon a mechanical movement.

One particular use of the transducer is in winding apparatus for controlling the torque applied to a winding spindle on which a thread, wire, tape, web or other filament is being wound in order to maintain the tension in the thread or other filament substantially constant. Such winding apparatus usually incorporates a dancer arm which rests on the thread or filament as it passes to the wind-up bobbin on which it is being wound. According to the present invention, movement of the dancer arm with variation in tension of the thread or filament causes movement of the member of a transducer as above described, thereby producing a varying output signal which can be applied to control the drive mechanism for the wind-up bobbin, in order to vary the driving torque so as to keep the tension in the thread or filament substantially at the correct value.

According to a preferred construction of the transducer, the two coil and core assemblies are mounted within a tubular housing of electrically insulating material, the interior wall of said housing carrying or being formed with a first locating means for the first coil and core assembly and a second locating means for the second coil and core assembly whereby to provide the desired gap between the adjacent ends of the cores and an aperture in the wall of said tubular housing through which a portion of the movable member can extend into the gap between the two cores. Preferably the tubular member is cylindrical.

Advantageously, the internal bore size of the tubular member varies in a series of steps from one end to the other, at least some of said steps serving as locating means for the coil and core assemblies.

The invention will now be further described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a block diagram illustrating one embodiment of transducer according to this invention and its associated circuitry,

FIGS. 2, 3 and 4 are diagrams illustrating the principle of .the transducer,

FIGS. 5:: and 5b show respectively plan and side elevational views illustrating the use of a transducer according to the invention in an apparatus for winding threads or other filaments,

FIG. 6 is an axial cross-section through a preferred construction of transducer according to this invention,

FIG. 7 is a side view of the transducer;

FIG. 8 is an end view; and

FIG. 9 is a schematic diagram of a control system for the winding apparatus of FIGS. 5a and 5b.

Referring to FIG. 1, the transducer comprises a primary winding 4 wound on a core 5 which can be of any low reluctance material such as soft iron, silicon steel or a ferrite material. The secondary winding 7 of the transducer is wound on a similar core 8. Between the coil and core assemblies is a movable member 6, which may be in the form of a vane made from an electrically conducting non-ferromagnetic metal, for example copper or aluminium.

The winding 4 is energized by an alternating voltage from any convenient signal source, here shown as an oscillator 2, whose output is fed through an amplifier 3 to the winding 4. The power supply for the circuits is shown at 1. The output from the secondary winding 7 is fed through a demodulator 9 to a load impedance 10. The load impedance may be part of a control system so that the output signal produced from the demodulator 9 effects a control function on the control system.

Referring now to FIGS. 2, 3 and 4, the two assemblies comprising the primary winding 4 and core 5 and secondary winding 7 and core 8 are shown separated by a gap. The magnetic flux paths extending between the two coil and core assemblies, when the coil 4 is energized, are shown at 11 and it will be seen that a strong field extends across the gap 12 between the two cores 5 and 8. FIG. 3 indicates the effect of introducing a portion of the vane 6 half-way between the two cores 5 and 8. The alternating flux produced by the primary winding 5 causes eddy currents to be produced in the vane 6, which in turn sets up its own magnetic field in such a direction as to oppose that field which caused the eddy current. The result is that the flux produced by the primary winding 4 is diverted away from the vane and hence away from the secondary winding 7, thus reducing the magnetic flux coupling between the coils and hence the amplitude of the signal generated in the coil 7. FIG. 4 shows the situation when the vane 6 is full inserted in the gap between the two assemblies, thus diverting all the flux and producing substantially no coupling between the primary and secondary coils and therefore no or only a very low value of output signal in the coil 7.

The pole faces of the cores 5 and 8 can be shaped to give any desired form of flux concentration while the vane, in conjunction with any given shape of pole face, may be so shaped and positioned to give any desired output voltage function with respect to the vane position.

It will be seen that the transducer described is of simple inexpensive and robust construction, the only moving part being the vane, which may be mounted on a simple bearing.

The function of the output signal as a position of the vane may be given any desired value dependent on the relative shapes of the vane and pole faces. Thus, it can be changed by shaping the vane, i.e. where linearity is only important about a small portion of the total travel, the vane could be a circular member pivoted off-center. Referring now to FIGS. 5a and 5b, there is illustrated one embodiment of part of a winding apparatus for winding a thread or other filament and incorporating a transducer according to this invention for controlling the torque of the drive to the winding spindle and hence the tension in the thread or other filament, as it is being wound. The two coil and core assemblies 4, 5 and 7, 8 of the transducer are shown mounted on a support 13 with a gap 12 between the 7 cores 5 and 8. The vane 6 of aluminum, for example, is mounted on a rotatable spindle 14 which also supports a dancer arm 15 carrying a roller 16 at its free end. The roller 16 rests on the thread or other filament 17 to be wound, on its passage to the wind-up bobbin 18 which is mounted on a drive spindle 19. The drive to the wind-up bobbin has its torque controlled, by means of an induction coupling device, for example, as disclosed in U.S. Pat. No. 3,054,006, issued Sept. II, 1962. Instead of an induction coupling, either a DC. or

AC. motor could be used. The dancer arm 15 serves to impart tension in the thread or filament due to the weight of the arm or some other force acting on the arm (e.g. by springs or additional weights or counter weights). This tension is balanced by a torque supplied to the drive spindle of the wind-up bobbin. Therefore, if the arm is maintained in a constant position, constant filament tension will result.

If the thread tension varies by either a change in filament delivery speed or wind-up bobbin speed, the arm moves away from a desired set position, thereby moving the position of the vane 6 relative to the gap 12 between the primary winding and secondary winding of the transducer. The transducer thus produces an output signal depending upon the position of the arm and this output signal is applied to control the torque supplied to the drive spindle of the wind-up bobbin in order to change its speed so that the dancer arm is returned to the desired set position.

If the tension in the thread or filament increases, it exerts a force on the roller on the dancer arm and rotates the spindle carrying this arm to move the vane more into the gap between the primary and secondary coils of the transducer. This in turn reduces the output signal from the transducer which operates to reduce the power to the induction coupling device and hence the torque applied to the drive spindle for the wind-up bobbin. This in turn reduces the tension in the thread or filament allowing the arm to return to the desired set position. The reverse action takes place when the tension in the thread or filament is decreased.

In this way substantially constant tension is maintained in the thread or filament as it is being wound, thereby greatly reducing the chance of breakage of thread or filament.

It should be understood that the above is a description of only one embodiment. Thus changes in relative arm movement/transducer output/ and drive torque as well as in the shape and arrangement of the parts may be made. Also the same principle can be applied to unwind systems and different arrangements for the filament path can be provided.

Moreover, the vane 6 of electrically conducting material may be a magnetic material, such as mild steel, although its effective action may not be so good as where it is made of nonmagnetic material.

FIG. 9 shows a schematic circuit diagram for a control system for the arrangement of FIGS. 5a and 5b.

Oscillator 40 provides an alternating voltage, preferably above SKI-I2, to the ferrite cored coil 4 of the transducer. Magnetic flux produced by coil 4 couples with the further ferrite cored coil 7, the amount of coupling depending on the position of the electrical conducting vane 6 between coils 4 and 7. The voltage induced by coil 4 into coil 7 is rectified by rectifier 41, smoothed by capacitor 42 and appears as a DC. voltage across resistor 43, the magnitude of this DC. voltage is dependent on the position of the electrically conducting vane 6. A preset voltage selected by potentiometer 44 is applied to an amplifier 45 by means of resistor 46. Potentiometer 44 serves as a control to set the height of the dancer roll 16.

The voltage appearing across resistor 43 is applied to amplifier 45 by means of resistors 47 and 48, capacitor 50 providing a lower impedance path for transient voltage changes appearing across resistor 43. These voltages across resistors 43 and 46 are of opposite polarity and are compared in the amplifier 45, the amplified difference of the two voltages'appearing at the output of amplifier 45 at terminal 51. Resistor 52 controls the gain of amplifier 45. The output voltage of amplifier 45 is fed into a thyristor firing circuit 53 which produces a pulse at terminal 54, the phase of which is dependent on the magnitude of the voltage appearing at terminal 51. This pulse is fed into the gate of a thyristor 55 which is part of a half-wave thyristor rectifier circuit comprising an excitation coil 56 in series with a thyristor 55 across an alternating voltage supply appearing across terminals 57 and 58.

Thus the current in coil 56 is proportional to the position of vane 6 and this coil is the excitation coil of the induction coupling driving the spindle 19. The torque of the coupling is dependent on the current flowing in coil 56 and hence on the vane position. Also connected to terminals 57 and 58 are power supplies 59 to provide the necessary voltages to the oscillator 40, amplifier 45 and firing circuit 53.

Referring now to FIGS. 6 to 8, a further embodiment of the transducer is shown, which comprises a tubular housing 21 of an electrical insulating material, for example a hollow cylindrical member formed from a plastics material. The internal bore of the housing is machined or otherwise shaped to form the steps 22, 23 and 24 as shown. The steps 22 and 24 form accurate locations for the holders 25 carrying the ferromagnetic cores 26 around which are disposed the coil assemblies 27. The coils are themselves carried by coil formers 28 located in recesses 29 in the ends of the holders 25. The step 23 is provided to facilitate insertion of the core 26 with its coil assembly 27.

Since the holders 25 are located by the steps 22 and 24 and provided that the cores 26 are accurately positioned in the holders, an accurate dimension for the gap 30, between the adjacent ends of the cores can be obtained. The wall of the housing 21 is provided with an aperture 31 opposite this gap through which can pass a portion of a metal vane forming the movable member of the transducer. The transducer assembly may be completed by plugs 32 to protect the ends of the assembly and if desired the assembly can be encapsulated for example in a suitable resin. Electrical connections to the coils of the transducer are made through terminals 33 carried by a terminal strip 34 mounted on the outside of the housing 21.

The wires 35 of the coils pass through small holes in the housing 21 and are secured to the terminals 33.

With this construction the parts of the transducer are protected to resist mechanical damage and shock. Moreover such a construction makes accurate assembly 'of the transducer a simple matter.

According to a modification, the tubular housing may be made of a sufficient length to accommodate a printed circuit board or microcircuit between each coil and core assembly and the adjacent plug 12. The circuits would be similar to those of FIG. 1 and comprise the oscillatorand possibly an amplifier on the input side and an amplifier and/or demodulator on the output side.

I claim:

1. In a winding apparatus, an arrangement for controlling the torque applied to a winding spindle on which a web or filament is being wound in order to maintain the tension in the web or filament substantially constant, the improvement comprising an electrical transducer having a first winding carried by a core of ferromagnetic material, a second winding coupled to said first winding and carried by a second core of ferromagnetic material which is spaced from said first core and a member of electrically conducting material which can be moved into and out of the gap between the cores, means for applying an alternating voltage to said first winding and means for deriving an output signal induced by said alternating voltage from said second winding, a dancer arm connected to the movable member and which rests on the web or filament when it is being wound, whereby movement of the dancer arm with variation in tension of the web or filament causes movement of the movable member of said transducer thereby varying the efiective coupling between said first and second coils and producing a varying output signal from said second coil, and means for applying said output signal to a rectifier circuit producing a direct voltage proportional to the position of the movable member, means for feeding the direct voltage to an amplifier, means for feeding said amplifier with a further signal representing the position of the dancer arm whereby said amplifier produces an output signal proportional to the difference between the signal from the transducer and the signal representing the position of the dancer arm, and means for applying said amplifier output signal to control the drive means to the winding spindle in order to keep the tension in the web or filament substantially at the correct value.

2. An arrangement as claimed in claim 1, wherein the output signal from the amplifier is fed to control a firing circuit for a controlled rectifier which produces a pulse whose phase depends on the magnitude of the output signal from the amplifier, and the controlled rectifier is in series with an energizing 5 winding of an induction coupling forming the drive means to the winding spindle, and said rectifier and winding are connected across an alternating voltage supply. 

1. In a winding apparatus, an arrangement for controlling the torque applied to a winding spindle on which a web or filament is being wound in order to maintain the tension in the web or filament substantially constant, the improvement comprising an electrical transducer having a first winding carried by a core of ferromagnetic material, a second winding coupled to said first winding and carried by a second core of ferromagnetic material which is spaced from said first core and a member of electrically conducting material which can be moved into and out of the gap between the cores, means for applying an alternating voltage to said first winding and means for deriving an output signal induced by said alternating voltage from said second winding, a dancer arm connected to the movable member and which rests on the web or filament when it is being wound, whereby movement of the dancer arm with variation in tension of the web or filament causes movement of the movable member of said transducer thereby varying the effective coupling between said first and second coils and producing a varying output signal from said second coil, and means for applying said output signal to a rectifier circuit producing a direct voltage proportional to the position of the movable member, means for feeding the direct voltage to an amplifier, means for feeding said amplifier with a further signal representing the position of the dancer arm whereby said amplifier produces an output signal proportional to the difference between the signal from the transducer and the signal representing the position of the dancer arm, and means for applying said amplifier output signal to control the drive means to the winding spindle in order to keep the tension in the web or filament substantially at the correct value.
 2. An arrangement as claimed in claim 1, wherein the output signal from the amplifier is fed to control a firing circuit for a controlled rectifier which produces a pulse whose phase depends on the magnitude of the output signal from the amplifier, and the controlled rectifier is in series with an energizing winding of an induction coupling forming the drive means to the winding spindle, and said rectifier and winding are connected across an alternating voltage supply. 